Heat exchanger and associated method for producing same

ABSTRACT

The present invention concerns a heat exchanger ( 1 ) comprising:
         a tube bundle ( 2 ) comprising a plurality of tubes ( 20 ) arranged parallel to each other and spacers ( 21 ) arranged between said tubes ( 20 ),   a collector plate ( 4 ) comprising holes ( 43 ) respectively bordered by first flanges ( 44 ) into which ends ( 22 ) of the tubes ( 20 ) are inserted,   the tube bundle ( 2 ) being brazed and the collector plate ( 4 ) comprising at least one compressible seal ( 41 ) forming second flanges ( 45 ), the second flanges ( 45 ) being compressed between the first flanges ( 43 ) and the ends ( 22 ) of the tubes ( 20 ) in order to provide a tight seal between said ends ( 22 ) of the tubes ( 20 ) and the corresponding first flanges ( 43 ).

The invention concerns a heat exchanger, in particular for a motor vehicle, and the method for producing same.

More particularly, it concerns a heat exchanger comprising a plurality of tubes between which spacers are inserted. The tubes are generally tubes with an oval or oblong cross section, defined by a major axis and a minor axis, and having ends inserted into holes of a collector plate. In order to ensure tight sealing and facilitate production, the tubes, the spacers and the collector plate are generally made from a metal material and attached together during a single brazing step.

However, during the use of the heat exchanger, the link between the tubes and the collector plate is rigid and cannot compensate for expansion and retraction phenomena resulting from temperature variations. Over time, these links weaken, and breakages or leaks can occur.

One of the aims of the present invention is therefore to at least partially overcome the problems of the prior art and propose an improved heat exchanger and the method for producing same.

The present invention therefore concerns a heat exchanger comprising:

-   -   a tube bundle comprising a plurality of tubes arranged parallel         to each other and spacers arranged between said tubes,     -   a collector plate comprising holes respectively bordered by         first flanges into which ends of the tubes are inserted,

the tube bundle being brazed and the collector plate comprising at least one compressible seal forming second flanges, the second flanges being compressed between the first flanges and the ends of the tubes in order to provide a tight seal between said ends of the tubes and the corresponding first flanges.

Using a compressible seal or a plurality of compressible seals to create the link between the bundle and the collector plate provides a certain flexibility that can absorb the expansions and retractions resulting from temperature variations. The link between the bundle and the collector plate is therefore more resistant to these temperature variations. There is a synergistic effect between the flexibility of the link, between the bundle and the collector plate plate, and the fact that the bundle is brazed. As a result of this, the heat exchanger offers optimum thermal performances, due to the brazed bundle, and improved resistance to temperature variations, due to the link between the bundle and the collector plate plate. Moreover, because the collector plate is not brazed, said collector plate can be thinner and there is less of a need to reinforce the collector.

According to one aspect of the invention, at least the end of each tube has an oblong cross section.

According to another aspect of the invention, the ends of the tubes comprise a first flaring and a bearing area compressing the compressible seal.

According to another aspect of the invention, the ends of the tubes comprise, in addition to or as an alternative to the first flaring, at least one second flaring extending above the compressible seal. It is therefore understood that the ends of the tubes can comprise the first flaring or the second flaring, separately, or indeed the first and the second flaring.

According to another aspect of the invention, the second flaring is produced over a limited portion of the ends of the tubes.

According to another aspect of the invention, the rate of compression of said second flanges is between 10% and 50% and preferably between 25% and 35%.

The invention also concerns a method for producing a heat exchanger as previously described and comprising the following steps:

-   -   a) assembling a tube bundle comprising a plurality of tubes         arranged parallel to each other and spacers arranged between         said tubes,     -   b) brazing the tubes to the spacers,     -   c) assembling a collector plate provided with holes bordered by         first flanges with a cross section corresponding to the ends of         the tubes and equipped with a compressible seal forming second         flanges suitable for being engaged respectively through the         holes,     -   d) inserting the ends of the tubes into the holes of the         collector plate so as to compress the second flanges of the         compressible seal.

According to one aspect of the method according to the invention, the step d) of inserting the ends of the tubes into the holes of the collector plate so as to compress the second flanges comprises a first sub-step of inserting the ends of the tubes into the holes of the collector plate and a second sub-step of producing a first flaring and a bearing area at the ends of the tubes.

According to another aspect of the method according to the invention, the step d) of inserting the ends of the tubes into the holes of the collector plate so as to compress the second flanges is a step of press-fitting the ends of the tubes into the holes of the collector plate, at least said ends being larger in size than the openings of the second flanges.

According to another aspect of the method according to the invention, the method comprises an additional step of producing at least one second flaring at the ends of the tubes extending above the compressible seal.

According to another aspect of the method according to the invention, the second flaring is produced over a limited portion of the ends of the tubes.

Other features and advantages of the invention will become clearer on reading the description that follows, provided as an illustrative and non-limiting example, and viewing the appended drawings in which:

FIG. 1 shows a schematic perspective view of a heat exchanger,

FIG. 2 shows a schematic cross-sectional perspective view of a heat exchanger,

FIG. 3 shows a schematic exploded cross-sectional view of a collector plate,

FIG. 3′ shows a schematic cross-sectional view of the collector plate of FIG. 3,

FIG. 4 shows a schematic view of the collector plate of FIG. 3 along the cutting plane XX,

FIG. 5 shows a schematic cross-sectional view of a heat exchanger according to a first embodiment,

FIGS. 6 to 8 show a schematic cross-sectional view of a heat exchanger according to a second embodiment during different steps of production.

The elements that are identical in the different figures have been given the same reference numbers.

The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference concerns the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

In the present description, certain elements or parameters may be numbered, for example as a first element or a second element, as a first parameter and a second parameter, or indeed a first criterion and a second criterion, etc. The purpose of this numbering is simply to differentiate between and designate elements, parameters or criteria that are similar but not identical. This numbering does not imply priority of one element, parameter or criterion over another, and such designations can easily be interchanged without departing from the context of the present description. Nor does this numbering imply an order in time, for example in teams of appraising such or such criteria.

The heat exchanger 1 shown in FIGS. 1 and 2 comprises a bundle 2 formed from a plurality of tubes 20 inside which a first heat-transfer fluid can flow. The tubes 20 are arranged parallel to each other and stacked. Between the tubes 20, spacers 21 are arranged, acting as interference devices and increasing the surface area for the exchange of heat with a second heat-transfer fluid passing between said tubes 20. The tubes 20 and spacers 21 are produced from a metal material and are brazed together in order to form the bundle 2. Having a brazed bundle 2 helps improve the thermal performances, i.e. the heat exchanges between the two heat-transfer fluids, compared to a mechanically assembled bundle. As shown in FIGS. 1 and 2, the tubes 20 preferably have an oblong and relatively flat shape. Moreover, the tubes 20 can have an internal spacer 26 between the inner walls of same. This spacer 26 helps provide said tubes 20 with a good level of rigidity.

The heat exchanger 1 also comprises two water collectors or tanks arranged at each end 22 of the tubes 20. These collectors comprise a collector plate 4 and a cover (not shown) that covers said collector plate 4 and closes the collector. These collectors are used to collect and/or distribute the first heat-transfer fluid in order for it to flow in the tubes 20.

As shown in greater detail in FIG. 3′, the collector plate 4 provides the sealed link between the collector and the brazed bundle 2. Said collector plate 4 comprises a core 40, that can be generally rectangular, delimiting a plurality of holes 43 that have a cross section that matches the shape of the cross section of the tubes 20 and that are capable of receiving the ends 22 of the tubes. Each hole 43 is bordered by a first flange 44 turned towards the inside of the bundle 2. The holes 43 are similar in size to the openings of the first flanges 44. The first flanges 44 can advantageously be formed as an integral part of the collector plate 4 and can be formed, for example, at the same time as the holes 43, by drawing.

Since the shape of the holes 43 and the first flanges 44 matches that of the cross section of the tubes 20, or at least the ends 22 of same, and this shape is generally oblong, it is possible to characterize said holes 43 and first flanges 44 according to two axes of different lengths. The length L1 corresponds to the longer length and can correspond to the width of the hole 43, as shown in FIGS. 3, 3′ and 5 to 8. The length 11 corresponds meanwhile to the shorter length and can correspond to the thickness of the hole 43, as shown in FIG. 4. In order to allow the ends 22 of the tubes 20 to be inserted into the first flanges 44, the lengths L1 and l1 of the hole 43 are larger than those of the ends 22 of the tubes 20. Reference made here to the width and thickness of the holes 43 reflects that made to the width and thickness of the tubes 20 that are intended to be inserted into said holes 43.

The core 40 is extended by a peripheral groove 42 that ends with a peripheral rim 46 forming foldable tabs. The peripheral groove 42 is intended to receive the rims of the cover, and the peripheral rim 46 can be folded to attach said cover onto the collector plate 4.

The collector plate 4 receives at least one compressible seal 41, in particular to ensure tight sealing at the holes 43.

According to a first embodiment, shown in FIGS. 1 and 2, the collector plate 4 can be provided with only a single compressible seal 41. This compressible seal 41 comprises a core that is applied against the core 40 of the collector plate 4. This core of the compressible seal 41 is linked to a plurality of second flanges 45, each of which is inserted into a hole 43. When the bundle 2 is assembled with the collector plate 4, the second flanges 45 are compressed between the first flanges 43 and the ends 22 in order to ensure tight sealing between said ends 22 of the tubes 20 and the corresponding first flanges 43. The rate of compression of the flanges 45 is 30%. According to variants of the invention, the rate is between 10% and 50% and preferably between 25% and 35%. Moreover, the core of the compressible seal 41 can form, at its periphery, a bead 47 arranged in the peripheral groove 42 and capable of providing a tight seal with the cover when the peripheral rim 46 is folded.

According to a second embodiment not shown here, the collector plate 4 can comprise a plurality of compressible seals 41 that form flanges 45 that are each inserted into a hole 43 in order to ensure tight sealing between the end 22 of a tube 20 and the corresponding first flange 43. In this embodiment, tight sealing with the cover can be ensured by a separate compressible seal positioned in the peripheral groove 42.

Using a compressible seal 41 or a plurality of compressible seals 41 for producing the link between the bundle 2 and the collector plate 4, provides a certain flexibility that can absorb the expansions and retractions resulting from temperature variations. The link between the bundle 2 and the collector plate 4 is therefore more resistant to these temperature variations. There is a synergistic effect between the flexibility of the link between the bundle 2 and the collector plate 4, and the fact that the bundle 2 is brazed. As a result of this, the heat exchanger 1 offers optimum thermal performances, due to the brazed bundle 2, and improved resistance to temperature variations, due to the link between the bundle 2 and the collector plate 4. Moreover, because the collector plate 4 is not brazed, said collector plate 4 can be thinner and there is less of a need to reinforce the collector.

The shape of the second flanges 45 also matches that of the cross section of the tubes 20, or at least the ends 22 of same. It is therefore possible to characterize said second flanges 45 according to two axes of different lengths. The length L2 corresponds to the width of the opening of the second flange 45 when the compressible seal 41 is not compressed, as shown in FIGS. 3, 3′, 4 and 6. The length 12 corresponds to the thickness of the opening of the second flange 45 when the compressible seal 41 is not compressed, as shown in FIG. 4. When compressed, the opening of the second flange 45 at at least one of these lengths (width and/or thickness) increases, for example as shown in FIGS. 5, 7 and 8, in which the width of the opening of the compressible seal 45 is larger and corresponds to a length L2′. As before, reference made here to the width and thickness of the openings of the second flanges 45 reflects that made to the width and thickness of the tubes 20 that are intended to be inserted into said openings of the second flanges 45.

The ends 22 of the tubes 20 are larger in size than the openings of the second flanges 45 but smaller in size than the holes 43 in order to compress the compressible seal 41 at the second flanges 45. Larger or smaller in size should be taken to mean that there is a difference at least in width and/or thickness between the tubes 20 and the holes 43 or the openings of the second flanges 45.

As shown in FIG. 5, the body of a tube 20 and its end 22 can be identical in width and thickness, i.e. the size (width and thickness) of the tube 20 is constant within the bundle 2. The compressible seal 41 is compressed because the width and the thickness of the tube 20 as a whole is larger than that of the openings of the second flanges 45 and smaller than that of the holes 43.

On the contrary, and as shown in FIGS. 7 and 8, the body of a tube 20 and its end 22 can have a different width and/or thickness. The end 22 can have a seal flaring 23 referred to hereinafter as the first flaring 23 on the inside of the bundle 2 and that increases the width and/or the thickness of said end 22. The end 22 also comprises a bearing area 24 that is wider and/or thicker than the rest of the body of the tube 20 as a result of the first flaring 23 and that compresses the compressible seal 41.

The ends 22 of the tubes 20 can also comprise, as an alternative or in addition to the first flaring 23, at least one second flaring 25—a retaining flaring allowing mechanical locking—on the outside of the bundle 2 and that extends over the compressible seal 41 as shown in FIGS. 1, 2 and 8. This second flaring 25 can be produced, in particular, over a limited portion of the ends 22 of the tubes 20. This second flaring 25 allows, in particular, the collector plate 4 to be immobilized and held in position on the bundle 2. In the example shown in FIGS. 1 and 2, the ends 22 of the tubes 20 each comprise two second flarings 25 produced over a limited portion. The first 23 and second 25 flarings of the ends 22 are situated to either side of the collector plate 4.

The present invention also concerns a method for producing a heat exchanger 1 as previously described and comprising the following steps:

-   -   a) assembling a tube bundle 2 comprising a plurality of tubes 20         arranged parallel to each other and spacers 21 arranged between         said tubes 20,     -   b) brazing the tubes 20 to the spacers 21,     -   c) assembling a collector plate 4 provided with holes 43         bordered by first flanges 44 with a cross section corresponding         to the ends 22 of the tubes 20 and equipped with a compressible         seal 41 forming second flanges 45 suitable for being engaged         respectively through the holes 43,     -   d) inserting the ends 22 of the tubes 20 into the holes 43 of         the collector plate 4 so as to compress the second flanges 45 of         the compressible seal 41.

According to one embodiment, and in particular when the size of the end 22 of the tubes 20 is smaller than or equal to the size of the opening of the second flanges 45, this last step d) can comprise a first sub-step of inserting the ends 22 of the tubes 20 into the holes 43 of the collector plate 4 and a second sub-step of producing the first flaring 23 and the bearing area 24 at the ends 22 of the tubes 20. This first sub-step is shown in FIG. 6, and the insertion is therefore easy to carry out because the end 22 of the tube 20 is smaller than or equal in size to the opening of the second flange 45, and the compressible seal 41 is compressed by forming the first flaring 23 and the bearing area 24, as shown in FIGS. 7 and 8. This first flaring 23 and the bearing area 24 can be produced, for example, by using a punch with a shape corresponding to that of the ends 22 of the tubes 20.

According to another embodiment, the step d) of inserting the ends 22 of the tubes 20 into the holes 43 of the collector plate 4 so as to compress the second flanges 45 of the compressible seal 41 can be a step of press-fitting the ends 22 of the tubes 20 into the holes 43 of the collector plate 4. In order for the compressible seal 41 to be compressed, at least the ends 22 of the tubes 20 are larger in size than the openings of the second flanges 45, either because the tube 20 as a whole is generally larger in size, as shown in FIG. 6, or because a first flaring 23 and a bearing area 24, as shown in FIGS. 7 and 8, have been produced in advance on the ends 22 of the tubes 20.

The production method can also comprise an additional step of producing at least one second flaring 25 extending above the compressible seal 41 as shown in FIGS. 1, 2 and 8. This second flaring 25 can be produced over a limited portion of the ends 22 of the tubes 20.

It is therefore clear that the heat exchanger 1 according to the invention offers optimum thermal performances, due to the brazed bundle 2, and improved resistance to temperature variations, due to the mechanical link between the bundle 2 and the collector plate 4. 

1. A heat exchanger comprising: a tube bundle comprising a plurality of tubes arranged parallel to each other and spacers arranged between said tubes; and a collector plate comprising holes respectively bordered by first flanges into which ends of the tubes are inserted, wherein the tube bundle is brazed and the collector plate comprises at least one compressible seal forming second flanges, the second flanges being compressed between the first flanges and the ends of the tubes in order to provide a tight seal between said ends of the tubes and the corresponding first flanges.
 2. The heat exchanger as claimed in claim 1, wherein at least the end of each tube has an oblong cross section.
 3. The heat exchanger as claimed in claim 1, wherein the ends of the tubes comprise a first flaring and a bearing area compressing the compressible seal.
 4. The heat exchanger as claimed in claim 1, wherein the ends of the tubes comprise at least one second flaring extending above the compressible seal.
 5. The heat exchanger as claimed in claim 4, wherein the second flaring is produced over a limited portion of the ends of the tubes.
 6. The heat exchanger as claimed in claim 1, wherein the rate of compression of said second flanges is between 25% and 35%.
 7. A method for producing a heat exchanger as claimed in claim 1, comprising the following steps: a) assembling a tube bundle comprising a plurality of tubes arranged parallel to each other and spacers arranged between said tubes, b) brazing the tubes to the spacers, c) assembling a collector plate provided with holes bordered by first flanges with a cross section corresponding to the ends of the tubes and equipped with a compressible seal forming second flanges suitable for being engaged respectively through the holes, d) inserting the ends of the tubes into the holes of the collector plate so as to compress the second flanges of the compressible seal.
 8. The method as claimed in claim 7, wherein the step d) of inserting the ends of the tubes into the holes of the collector plate so as to compress the second flanges comprises a first sub-step of inserting the ends of the tubes into the holes of the collector plate and a second sub-step of producing a first flaring and a bearing area at the ends of the tubes.
 9. The method as claimed in claim 7, wherein the step d) of inserting the ends of the tubes into the holes of the collector plate so as to compress the second flanges comprises a step of press-fitting the ends of the tubes into the holes of the collector plate, at least said ends being larger in size than the openings of the second flanges.
 10. The method as claimed in claim 7, further comprising an additional step of producing at least one second flaring at the ends of the tubes extending above the compressible seal.
 11. The method as claimed in claim 10, wherein the second flaring is produced over a limited portion of the ends of the tubes. 